1. Field of the Invention
The present invention relates to a liquid-crystal display panel and to a method for manufacturing a liquid-crystal display panel, and more particularly it relates to a liquid-crystal display panel with improved accuracy in the gap between panels and in which deterioration of display characteristics such as contrast is prevented, and to a method for manufacturing such a liquid-crystal display panel.
2. Description about the Related Arts
In the past, liquid-crystal display panels, both color and monochrome types, have found widespread use as a means for displaying information.
In such a liquid-crystal display panel, the achievement of a uniform gap between panels assembled in the display is important.
To achieve that end, spherical gap material known as micropearls, made of acrylic resin or SiO2 are generally dispersed onto the glass substrate on which TFTs are formed, after which the opposing glass substrate is placed thereover.
In the above-noted method, however, because the micropearls that serve as the gap material are dispersed impartially on the display elements and interconnects, an electrical charge or the like on the glass substrates can cause variation in the distribution of the micropearls, thereby resulting in non-uniformity in the gap in the panel.
Another phenomenon is the collection of micropearls in the depressed aperture part of the glass substrate, thereby disturbing the orientation of the liquid crystal and leading to such problems as a loss of display contrast, which lowers the display quality.
Given the above-noted problems, there is in Japanese Unexamined Patent Publication (KOKAI) No. 10-282327, a disclosure of a non-conductive substance formed into a columnar shape to serve as gap spacers in a non-display region on a glass filter.
In the Japanese Unexamined Patent Publication (KOKAI) No. S60-164723, there is a disclosure of the formation of an insulating substance into a columnar shape on a TFT.
As a similar technology, there is a disclosure of the formation of an insulating substance into a columnar shape in the same manner over display interconnects of a TFT substrate.
The above-noted technologies eliminate the micropearls from the display region, and form gap spacers in locations corresponding to areas above the TFTs or interconnects other than the aperture part with a uniform density, so that in liquid-crystal panel having independent color filter and TFT substrates, there is an improvement in contrast, and even when spacers are formed, because these are in relatively thin parts, the accuracy of the gap between the panel surfaces is improved, thereby achieving the effect of improving the display quality.
The above-noted disclosed technologies, however, actually lead to another problem of non-uniformity in the gap within the panel, in that this is a CF-on-TFT (color filter on TFT) panel.
In CF-on-TFT technology, a color layer is formed directly on the TFT aperture part, so as to eliminate the reduction of the numerical aperture occurring because of offset in the alignment of the color filter substrate and the TFT substrate at the time of alignment, and is an effective technology with respect to achieving large glass substrates, a expanded display area, and fine display pixels.
In the prior art, because of the CF-on-TFT structure, each color layer, as shown in FIG. 4, must be formed so as to extend to the TFT signal electrode lines and the gate electrode lines.
Additionally, in order to eliminate metallic reflections from interconnects of external light, a black matrix is formed, not only over the TFTs, but also over the signal electrode lines and the gate electrode lines. Considering the positioning accuracy between the TFT and the various lines, the color layers and black matrix, pattern application methods such as the pigment distribution method, the printing method, the electrical deposition method, and the ink-jet method are applied.
With the above-noted pattern application methods, however, each time one layer is formed a variation in film thickness of 01. to 0.2 μm occurs within the panel, this variation tending to be particularly large over interconnects and the TFTs.
For this reason, in a CF-on-TFT panel, if columnar spacers 403 re formed as gap spacers over the TFTs and interconnects, there is an interaction between the black matrix and the color layers and the variation in application of the columnar spacers with acts to worsen the uniformity of the gap between the panel surfaces.
In Japanese Unexamined Patent Publication (KOKAI) No. 4-226424, there is a disclosure of technology for making the spacers or the like a metal light-blocking layer having aluminum as the main component when assembling a piece of electronic equipment having spacers or the like, and in Japanese Unexamined Patent Publication (KOKAI) No. 4-318816, there is language describing a liquid-crystal display panel with a spacer disposed in the liquid-crystal region between a color filter and the opposing substrate.
In neither of these disclosures, however, is there language with regard to forming an disposing columnar spacers in parts of the film having uniform thickness.
Accordingly, in order to improve upon the above-noted drawbacks in the prior art, it is an object of the present invention to provide a liquid-crystal display panel, including a color liquid-crystal display panel, which has a gap of superior uniformity within the panel, without a worsening of display characteristics such as contrast.